IFNAR1 and neoplasm: In this study, we determined that IFNβ upregulates PD-1 expression and knocks out IFNAR1-suppressed PD-1 expression in myeloid cells, revealing that PD-1 expression is regulated by IFN-I/IFNβ at least in part through an autocrine mechanism in myeloid cells in vitro and in tumor-bearing mice in vivo.